Lecture 20 BIO 311D 2nd Edition Outline of Last Lecture I Recap hormone experiments II Mutualism with N fixing bacteria III Plant defenses Outline of Current Lecture I Plant Defenses II Evolution of plant reproduction Current Lecture I Plant Defenses A Discuss two strategies one structural adaptation and one biochemical adaptation used by plants to deter herbivores Describe plant strategies to defend against pathogens Cactus thorns discourages herbivores from eating from it and reduces loss of water Trichomes B Plant Enemies and Defenses Plant defensive responses can be constitutive always present or induced produced in response to damage or stress Nicotine Alkaloids Tannins Pyrethrin Digitalis Latex C Plants such as milkweeds produce sticky latex and other substances to deter herbivores but Monarch caterpillars D Response to herbivore damage pathway to gene activation and production of defensive compounds Plant secondary compounds are toxic to insects 1 Wounding Chemical in saliva caterpillar lands on the plant 2 Signal transduction pathway caterpillar 3 Synthesis and release of volatile attractants caterpillar 4 Recruitment of parasitoid wasps that lay their eggs within caterpillars moth E Plant cells can have receptors that directly detect molecules from pathogens and trigger signal transduction In response cells turn on genes for production of antimicrobial proteins and also release alarm signals F Hypersensitive response damaged tissue sends signal so other tissues acquire resistance remain free of microbe the pathogen is contained and prevented from spreading when cells around it seal it off then die Infected cells produce anti microbial compounds Infected cells close off plasmodesmata and thicken cell walls Plant warning signals released into phloem included salicylic acid G Develop a scenario i e list a series of steps of adaptation by natural selection in which there is an evolutionary arms race between a plant and either 1 An herbivore or 2 A pathogenic microbe Plant would develop a poison that could harm the herbivore caterpillar beetle etc Plant evolves as the herbivores develop counter strategies Why don t all plants produce distasteful or noxious compounds in their leaves to discourage animal herbivores II H Phytochemicals compounds produced by plants but not considered essential nutrients Antioxidants Defenses against bacteria viruses fungi Defenses against herbivorous animals People are taking advantage of these plant defensive compounds using many as nutritional supplements to fight human disease Evolution of Plant Reproduction A Plant reproduction relies on intra species inter species and intercellular communication B Asexual reproduction vegetative by budding or fragmentation by runners or root spreading Quaking Aspen trees many individuals in a clone connected by their roots C Sexual life cycles always involve meiosis and fertilization What is the pattern for plant life cycles D Angiosperms a flower is the sexual reproduction of Angiosperms Monocots flower parts in 3 s Dicots flower parts in 4 s and 5 s or multiples Flower Parts are part of the diploid sporophyte generation Petals for attracting pollinators Sepals for protection or attraction Carpel with ovary egg production Anthers on stamen pollen production E A gametophyte is a multicellular haploid plant In vascular plants the gametophyte is tiny In flowering plants Male gametophyte is the pollen grain a few haploid cells Pollen grain is NOT the sperm nucleus The pollen grain doesn t fertilize It is part of pollination Female gametophyte is the embryo sac contains 8 haploid nuclei a few cells F Big picture of alternation of generations in flowering plants What is the diploid sporophyte What is the haploid gametophyte The alternation of generations life cycle in a flowering plant Sporophyte diploid meiosis gametophyte gametes fertilization diploid zygote
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